Direct reduction process using a single fluidised bed

ABSTRACT

A direct reduction process for a metalliferous material includes supplying the metalliferous material, a solid carbonaceous material, an oxygen-containing gas, and a fluidizing gas into a fluidized bed in a vessel and maintaining the fluidized bed in the vessel, at least partially reducing metalliferous material in the vessel, and discharging a product stream that includes the partially reduced metalliferous material from the vessel. The process comprises (a) reducing the metalliferous material in a solid state in a metal-rich zone in the vessel; (b) injecting the oxygen-containing gas into a carbon-rich zone in the vessel with a downward flow in a range of ±40° to the vertical and generating heat by reactions between oxygen and the metalliferous material (including metallized material), the solid carbonaceous material and other oxidizable solids and gases in the fluidized bed, and (c) transferring heat from the carbon-rich zone to the metal-rich zone by movement of solids within the vessel. The metal-rich zone is formed in a lower section of the vessel and the carbon-rich zone is an intermediate section below an upper section of the vessel. Oxygen-containing gas is injected into a central region of the vessel.

This is a national stage application filed under 35 USC 371 based onInternational Application No. PCT/EP2005/005472 filed May 20, 2005, andclaims priority under 35 USC 119 of Australian Patent Application No.2004902900 filed May 31, 2004.

The present invention relates to a direct reduction process for ametalliferous feed material, particularly, although by no meansexclusively, to a direct reduction process for an iron-containing feedmaterial, such as iron ore.

The present invention also relates to a process for reducing ametalliferous feed material that comprises a direct reduction processfor partially reducing metalliferous feed material in the solid stateand a smelting process for melting and further reducing the partiallyreduced metalliferous feed material to a molten metal.

The present invention was made during the course of an on-going researchproject carried out by the applicant to develop the so called “CIRCOFERtechnology” for the direct reduction of iron ore.

CIRCOFER technology is a direct reduction process that is capable ofreducing iron ore in the solid state to a metallisation of 50% orhigher.

CIRCOFER technology is based on the use of fluidised beds. The main feedmaterials to the fluidised beds are fluidising gas, metal oxides(typically iron ore fines), solid carbonaceous material (typically coal)and oxygen-containing gas (typically oxygen gas). The main productproduced in the fluidised beds is metallised metal oxides, i.e. metaloxides that have been at least partially reduced.

One of the findings of the applicant in the research project is that itis possible to establish separate reaction zones within a singlefluidised bed and to optimise the reactions in these zones. One reactionzone is a carbon-rich zone in which solid carbonaceous material, such ascoal, and other oxidisable reactants are oxidised and generate heat. Theother reaction zone is a metal-rich zone in which metalliferous feedmaterial, such as iron ore, is reduced in the solid state. The tworeaction zones are spaced apart within the fluidised bed, with themetal-rich zone typically being in a lower section and the carbon-richzone being spaced above the metal-rich zone. The zones may becontiguous. The fluidised bed comprises upward and downward flows ofsolids and this movement of material facilitates transfer of heatgenerated in the carbon-rich zone to the metal-rich zone and maintainsthe metal-rich zone at a temperature required for reducing themetalliferous feed material.

According to the present invention there is provided a direct reductionprocess for a metalliferous material which comprises supplying themetalliferous material, a solid carbonaceous material, anoxygen-containing gas, and a fluidising gas into a fluidised bed in avessel and maintaining the fluidised bed in the vessel, at leastpartially reducing metalliferous material in the vessel, and discharginga product stream that comprises the at least partially reducedmetalliferous material from the vessel, which process is characterisedby: (a) reducing the metalliferous material in a solid state in ametal-rich zone in the vessel; (b) injecting the oxygen-containing gasinto a carbon-rich zone in the vessel with a downward flow in a range ofplus or minus 40 degrees to the vertical and generating heat byreactions between oxygen and the metalliferous material (includingmetallised material), the solid carbonaceous material and otheroxidisable solids and gases in the fluidised bed, and (c) transferringheat from the carbon-rich zone to the metal-rich zone by movement ofsolids within the vessel.

Preferably the process comprises injecting the oxygen-containing gaswith a downward flow in a range of plus or minus fifteen degrees to thevertical.

The term “carbon-rich” zone is understood herein to mean a region in thefluidised bed in which there is a relatively large amount ofcarbon-containing material in relation to the amount of metalliferousmaterial than in other regions of the fluidised bed.

The term “metal-rich” zone is understood herein to mean a region in thefluidised bed in which there is a relatively large amount ofmetalliferous material in relation to the amount of carbon-containingmaterial than in other regions of the fluidised bed.

Preferably the process comprises forming the metal-rich zone in a lowersection of the vessel and the carbon-rich zone in an intermediatesection of the vessel.

Preferably the intermediate section is intermediate said lower sectionand an upper section of the vessel.

Preferably the process comprises injecting the oxygen-containing gasinto a central region in the vessel, i.e. a region that is locatedinwardly of a side wall of the vessel.

Preferably the process comprises controlling the temperature differencebetween the bulk temperature in the fluidised bed and the averagetemperature of the inwardly facing surface of a side wall of the vesselto be no more than a 100° C.

The term “bulk temperature” is understood herein to mean the averagetemperature throughout the fluidised bed.

More preferably the temperature difference is no more than 50° C.

In the case of reducing metalliferous material in the form of iron orefines, preferably the bulk temperature in the fluidised bed is in therange 850° C. to 1000° C.

Preferably the bulk temperature in the fluidised bed is at least 900°C., more preferably at least 950° C.

In addition, preferably the process comprises controlling thetemperature variation to be less than 50° C. within the fluidised bed.

The temperature difference may be controlled by controlling a number offactors including, by way of example, the amounts of the solids and thegases supplied to the vessel.

Furthermore, in the case of reducing metalliferous material in the formof iron ore fines, preferably the process comprises controlling thepressure in the vessel to be in the range of 1-10 bar absolute andpreferably 4-8 bar absolute.

Preferably the process comprises injecting the oxygen-containing gas sothat there is a downward flow of the gas in the vessel.

Preferably the process comprises injecting the oxygen-containing gas viaat least one lance having a lance tip with an outlet positioned in thevessel inwardly of the side wall of the vessel in the central region ofthe vessel.

Preferably the lance tip is directed downwardly.

More preferably the lance tip is directed vertically downwardly.

The position of the lance and, more particularly, the height of theoutlet of the lance tip, is determined by reference to factors, such asthe oxygen-containing gas injection velocity, the vessel pressure, theselection and amounts of the other feed materials to the vessel, and thefluidised bed density.

Preferably the process comprises water-cooling at least the lance tip tominimise the possibility of accretions forming on the lance tip thatcould block the injection of the oxygen-containing gas.

Preferably the process comprises water cooling an outer surface of thelance. Preferably the process comprises injecting the oxygen-containinggas through a central pipe of the lance.

Preferably the process comprises injecting the oxygen-containing gaswith sufficient velocity to form a substantially solids-free zone in theregion of the lance tip to minimise the formation of accretions on thelance tip that could block the injection of the oxygen-containing gas.

Preferably the process comprises injecting nitrogen and/or steam and/orother suitable shrouding gas and shrouding the region of the outlet ofthe lance tip to minimise oxidation of metal that could result inaccretions forming on the lance tip that could block the injection ofthe oxygen-containing gas.

Preferably the process comprises injecting the shrouding gas into thevessel at a velocity that is at least 60% of the velocity of theoxygen-containing gas.

Preferably the process comprises supplying the metalliferous feedmaterial, the carbonaceous material, the oxygen-containing gas, and thefluidising gas to the fluidised bed and maintaining the fluidised bedwith (a) a downward flow of the oxygen-containing gas, (b) an upwardflow of solids and fluidising gas countercurrent to the downward flow ofthe oxygen-containing gas, and (c) a downward flow of solids outwardlyof the upward flow of solids and fluidising gas.

In the fluidised bed described in the preceding paragraph, solids in theupward and downward flows of solids are heated by heat generated byreactions between the oxygen-containing gas, the solid carbonaceousmaterial and other oxidisable materials (such as CO, volatiles, and H₂)in the carbon-rich zone. The solids in the downward flow of solidstransfer heat to the metal-rich zone.

In addition, the upward and downward flows of solids shield the sidewall of the vessel from radiant heat generated by reactions between theoxygen-containing gas and the solid carbonaceous material and otheroxidisable solids and gases in the fluidised bed.

In the case of reducing metalliferous material in the form of iron orefines, preferably the fines are sized at minus 6 mm.

Preferably the fines have an average particle size in the range of 0.1to 0.8 mm.

One of the advantages of the process is that it can accept a substantialamount of metalliferous feed material with a particle size of less than100 microns without a significant amount of this material exiting theprocess entrained in off-gas. This is believed to be due to anagglomeration mechanism operating within the fluidised bed that promotesa desirable level of agglomeration between particles of feed materials,particularly sub-100 micron particles, without appearing to promoteuncontrolled agglomeration capable of interrupting operation of thefluidised bed. Similarly, friable ores that have a tendency to breakdown during processing and to thereby increase the proportion ofparticles in the fluidised bed with a size of less than 100 microns maybe processed without significant loss of feed material in processoff-gas.

Preferably the carbonaceous material is coal. In such a situation, theprocess devolatilises the coal to char and at least part of the charreacts with oxygen and forms CO in the fluidised bed.

Preferably the fluidising gas comprises a reducing gas, such as CO andH₂.

Preferably the process comprises selecting the amount of H₂ in thefluidising gas to be at least 15% by volume of the total volume of COand H₂ in the gas.

Preferably the process comprises discharging the product streamcomprising at least partially reduced metalliferous material from thelower section of the vessel.

Preferably the product stream also comprises other solids (for examplechar).

Preferably the process comprises separating at least a portion of theother solids from the product stream.

Preferably the process comprises returning the separated solids to thevessel.

Preferably the process comprises discharging an off-gas streamcontaining entrained solids from an upper section of the vessel.

Preferably the process comprises separating solids from the off-gasstream.

Preferably the process comprises maintaining a circulating fluidised bedby separating entrained solids from the off-gas stream and returning thesolids separated from the off-gas to the vessel.

Preferably the process comprises returning solids separated from theoff-gas to the lower portion of the vessel.

Preferably the process comprises preheating metalliferous feed materialwith the off-gas from the vessel.

Preferably the process comprises treating the off-gas after thepreheating step and returning at least a portion of the treated off-gasto the vessel as the fluidising gas.

Preferably the off-gas treatment comprises one or more of (a) solidsremoval, (b) cooling, (c) H₂O removal; (d) CO₂ removal, (e) compression,and (f) reheating.

Preferably the off-gas treatment comprises returning solids to thevessel.

The process may be operated to produce a product stream ranging from lowto high metallisation depending on the downstream requirements for theat least partially reduced metalliferous material. The metallisation mayrange from 30 to in excess of 80%. In situations in which metallisationgreater than 50% is required, preferably the process comprises operatingwith reducing gas in the fluidising gas. One option for the fluidisinggas in this instance is treated off-gas from the vessel. In situationsin which metallisation less than 50% is required, it is envisaged thatit will not be necessary to operate with reducing gas in the fluidisinggas and sufficient reductant can be obtained via solid carbonaceousmaterial supplied to the process.

The oxygen-containing gas may be any suitable gas.

Preferably the oxygen-containing gas comprises at least 90% by volumeoxygen.

According to the present invention there is also provided a process forreducing a metalliferous material that comprises (a) a direct reductionprocess for partially reducing metalliferous material in a solid stateas described herein and (b) a smelting process for melting and furtherreducing the partially reduced metalliferous material to a molten metal.

The present invention is described further with reference to theaccompany drawings, of which:

FIG. 1 is a diagram of an apparatus for direct reduction of ametalliferous material by one embodiment of a process in accordance withthe present invention which illustrates the reaction zones formed by theprocess within the vessel shown in the Figure; and

FIG. 2 is the same basic diagram as that shown in FIG. 1 whichillustrates the movement of solids and gases in the vessel caused by theprocess.

The following description is in the context of direct reduction of ametalliferous material in the form of iron ore particles in the solidstate. The present invention is not so limited and extends to directreduction of other iron-containing materials (such as ilmenite) and moregenerally to other metalliferous materials.

The following description is also in the context of direct reduction ofiron ore with coal as a solid carbonaceous material, oxygen as anoxygen-containing gas, and a mixture of at least CO, and H₂ as afluidising gas. The present invention is not so limited and extends tothe use of any other suitable solid carbonaceous material,oxygen-containing gas, and fluidising gas.

With reference to the Figures, the solid feed materials, namely iron orefines and coal, oxygen and fluidising gas are supplied to the vessel 3shown in the Figures and establish a fluidised bed in the vessel.

The solid feed materials are supplied to the vessel via a solidsdelivery device such as screw feed or solids injection lance 5 thatextends through a side wall 7 of the vessel.

The oxygen is injected into the vessel via a lance 9 having an outletlocated within a downwardly extending lance tip 11 that directs theoxygen downwardly in a central region 31 (FIG. 2) of the vessel. Thecentral region extends radially from a central axis of the vessel towardthe vessel wall. The oxygen is injected so as to have a downward flowdirected in the range between vertical and forty degrees to the verticalbut is preferably within the range of vertical to fifteen degrees to thevertical. Solids within the region of the lance outlet may becomeentrained in the oxygen flow. The interaction between the substantiallydownward flow of oxygen and the substantially upward flow of fluidisinggas is believed to significantly reduce the tendency for particlesentrained in the oxygen flow to contact side walls of the vessel andform accretions.

The fluidising gas is injected via a series of tuyeres or nozzles (notshown) in a base 13 of the vessel.

The above-described supply of solids and gases produces an upward flowof fluidising gas and entrained solids in the central region of thevessel. Increasingly, as the solids move upwardly, the solids disengagefrom the upward stream of fluidising gas and flow downwardly in anannular region between the central region and the side wall of thevessel. These recirculated solids are either entrained again in theupward stream of fluidising gas or are discharged from the vessel. Thismovement of material in the vessel is illustrated in FIG. 2.

The above-described supply of solids and gases also produces thefollowing reactions in the vessel.

Devolatilisation of coal to char and decomposition of coal volatiles togaseous products (such as H₂ and CO) and reaction of at least part ofthe char with oxygen to form CO.

Direct reduction of iron ore to at least partially reduced iron ore bygaseous products CO and H₂. These reactions in turn produce CO₂ and H₂O.

Reaction of part of the CO₂ with carbon to form CO (Boudouard reaction).

Oxidation of solids and gases such as char and particles of partiallyreduced metalliferous feed material, coal volatiles, CO, and H₂ withoxygen, which generates heat and promotes controlled agglomeration ofsmaller partially reduced ore particles with other particles within thefluidised bed.

The relative densities of the solids and the above-described injectionof the solids and the gases, including the locations of the solids/gasinjection, results in the formation of reaction zones within the vessel.The reaction zones may be contiguous.

One reaction zone is a carbon-rich zone 17 in the region of the lancetip 11 of the lance 9. In this zone the predominant reactions areoxidizing reactions involving combustion of char, coal volatiles, CO,and H₂ with oxygen which generate heat.

The other reaction zone is a metal-rich zone 19 in which (a) coal isdevolatilised and forms char and coal volatiles and (b) iron ore finesare at least partially reduced by CO and H₂.

The above-described downward flow of solids in the annular regionbetween the central region and the side wall facilitates transfer ofheat from the carbon-rich zone to the metal rich zone.

In addition, the downward flow of solids partially shields the side wallfrom direct exposure to radiant heat from the central region of thevessel.

The above-described process also produces a stream of off-gas andentrained solids that is discharged from the vessel via an outlet 27 inan upper section of the vessel. The off-gas stream is processed byseparating solids from the off-gas and returning the separated solids tothe vessel via a solids return leg 29. Thereafter, the off-gas istreated by a series of steps of including (a) solids removal, (b)cooling the off-gas, (c) H₂O removal, (d) CO₂ removal, (e) compression,and (f) reheating. The treated off-gas is thereafter returned to thevessel as part of the fluidising gas.

The above-described process produces a stream of solids, including atleast partially reduced iron ore and char, that is discharged from thevessel via an outlet 25 in the base of the vessel. The solids stream maybe processed by separating the at least partially reduced iron ore and aportion of the other solids. The other solids, predominantly char,separated from the product steam may also be returned to the vessel as apart of the solids feed for the process. The at least partially reducediron ore is further processed as required. By way of example, the atleast partially reduced iron ore may be supplied to a molten bath-basedsmelting vessel and smelted to molten iron, for example by a processsuch as the so called “Hlsmelt process”.

As is indicated above, the present invention was made during the courseof an ongoing research project carried out by the applicant to developCIRCOFER technology for the direct reduction of iron ore. The researchproject included a series of pilot plant runs on 350 mm diameter and 700mm diameter pilot plant set-ups of the applicant.

The following discussion focuses on research work on the 700 mm diametervessel pilot plant.

The pilot plant comprises an apparatus of the type shown in FIGS. 1 and2. The pilot plant was operated as a circulating fluidised bed atatmospheric pressure. The vessel has a height of 10.7 m. An uppersection of the vessel has a height of approximately 8.9 m and aninternal diameter of 700 mm. A lower section of the vessel has a heightof approximately 1.8 m and an internal diameter of 500 mm. This heightof 1.8 m includes the height of a fluidising grate and a transitionsection between the 500 mm diameter and the 700 mm diameter sections.The vessel is refractory lined.

Off-gas from the vessel was processed to remove entrained solids bypassing the off-gas successively through 3 cyclones connected in series.The first cyclone (cyclone 1) received off-gas directly from the vessel.Solids separated in the cyclone were returned to the vessel via a sealpot that provided for pressure sealing. The second cyclone (cyclone 2)received off-gas from cyclone 1. Solids separated in the cyclone werereturned to the vessel via a direct return of solids (i.e. no seal pot).The third cyclone (cyclone 3) received off-gas from the second 2. Solidsseparated by cyclone 3 were not returned to the vessel.

After solids separation by the three cyclones, the off-gas was furthertreated by a radial flow scrubber, which further removed solids from theoff-gas. These solids were concentrated by a thickener and then passedthrough a drum filter to produce thickener sludge.

Off-gas leaving the radial flow scrubber was then treated by a tubecooler that operated to dewater the off-gas by cooling it to within therange 10-30° C. Following treatment by the tube cooler, the off-gas wascombusted.

The fluidised bed was fluidised by air during the initial stages oftesting and was later fluidised by a mixture of nitrogen and hydrogengas. As there were no provisions for processing and recycling theprocess off-gas, e.g. CO₂ removal and compression, it was not possiblefor it to be returned to the vessel as fluidising gas. In this regard,hydrogen gas was used to simulate the effect of using processed off-gasas fluidising gas.

In summary, the research work demonstrated the following:

The concept of a coal based fluidised bed reduction process with oxygeninjection, producing a reduced product with metallisation levels of upto 78%.

Injecting oxygen into/or close to a fluidised bed with up to 42%metallic iron in the bed appears to be feasible without the formation ofaccretions.

The concept of simultaneously reducing iron ore and partially burningcoal for energy in a single bed vessel appears to be feasible, atmetallic iron loadings up to 48% in the product.

The position of the oxygen lance in the vessel is important because ofthe desirability of transferring the heat of oxidation back into the bedwhile minimising the level of iron reoxidation. The 4-m position isabout right for the conditions tested.

High phosphorus Brockman iron ore was successfully fluidised and reducedwithout excessive dust make. (Brockman ore is a friable West Australianiron ore made available by Hamersley Iron Pty Ltd, Perth, WesternAustralia.)

Objectives of the Experimental Program:

The primary objective was to achieve stable operation for a significantamount of time with high phosphorus Brockman ore (−3 mm) and Blair Atholcoal.

The plan was to operate with low iron ore feed (up to 20% in productdischarge) for two days with the oxygen lance in a low position (1.9-mabove the distributor plate (not shown in the Figure) of the vessel. Theaim was then to operate for three days with high ore feed (up to 70% inthe product) with the oxygen lance in an upper position (3.8-m above thedistributor plate).

Start-up:

The campaign started on the 9 Dec. 2003 at 0600 hrs with a gradual heatup of the 700-mm vessel (hereinafter also referred to as a “CFB”) usingalumina as the bed material. Once the target temperature was reached,coal and oxygen were introduced into the vessel at 1550 hrs. The oxygenrate was increased up to 105 Nm³/hr while the coal rate was in the range300-450 kg/hr.

Operation with Coal and Oxygen 10 Dec. 2003-11 Dec. 2003

Operation with coal, air and oxygen was conducted on 10 Dec. 2003. Theoperation was very smooth with the system stabilising fairly quickly andthe vessel maintaining its temperature of 900-930° C. without anyproblems.

The standard operating conditions during this period were as follows.

CFB temperature: 930° C. bottom and 900° C. top

Fluidising gas flowrate: 140 Nm³/hr (N₂) and 300 Nm³/hr (air)

Pressure drop CFB: 80-140 mbar

Oxygen flowrate: up to 100 Nm³/hr

N₂ shield gas flowrate: 30 Nm³/hr

Coal Feed Rate: 340-450 kg/hr

A summary of the results is as follows:

Bed Discharge Rate: 100-160 kg/hr

Cyclone 3 Discharge: 10-14 kg/hr

Offgas Analysis

CO/CO₂ 12.8/8.7 = 1.47 % H₂ 7.6 % CH₄ 0.7

The discharge product was clean with only some small +2 mm pieces whichlooked like residual refractory material. The dust make was reasonablylow with <10% of the discharge reporting to the final cyclone discharge.

Operation with Iron Ore (10-140 kg/hr), Coal and Oxygen (lance 2-mheight) 10 Dec. 2003-12 Dec. 2003

10 Dec. 2003 2200-11 Dec. 2003 0600: Iron Ore at 10 kq/hr

Iron ore (<3-mm) was introduced into the feed system at 2200 on 10 Dec.2003 at a rate of 10 kg-hr. Hydrogen was also introduced into thefluidising gas at a rate of 20 Nm³/hr to simulate use of processedoff-gas as fluidising gas. The operation was smooth with the bed ΔPbeing maintained at about 100-120 mbar and the temperature profilehaving a range of only 10° C. between the bottom and the top of the bed.

The product appeared fine without any signs of accretions oragglomerates. However, on screening the product (at 2 mm) some largerscale type material was found but this was only a very small proportionof the overall product. The scale appeared to be made up of ash/char andprobably formed on the walls of the vessel or distributor plate in thevessel.

The standard operating conditions and results during this period were asfollows.

CFB temperatures: 930° C. bottom and 900° C. top

Fluidising gas flowrate: 350 Nm³/hr (N₂) and 20 Nm³/hr (H₂)

Pressure drop CFB: 100-130 mbar

Oxygen flowrate: 100-115 Nm³/hr

N₂ shield gas flowrate: 30 Nm³/hr

Coal Feed Rate: 280-360 kg/hr

Iron Ore Feed Rate: 10 kg/hr

A summary of the results is as follows:

Bed Discharge Rate: 125 kg/hr

Cyclone Discharge: 15 kg/hr

Offgas Analysis

CO/CO₂ 10.3/9.7 = 1.06 % H₂ 9.2 % CH₄ 2.0

11 Dec. 2003 0600-11 Dec. 2003 1200: Iron Ore at 20 kg/hr

The iron ore feed rate was increased up to 20 kg/hr at 0600 on 11 Dec.2003 until 1200 11 Dec. 2003 and the hydrogen gas rate was alsoincreased up to 40 Nm³/hr. The operation continued to be smooth withoutany disruptions. The vessel bed pressure was being maintained at about80-100 mbar and the temperature profile had a range of only 10° C.between the bottom and the top of the bed.

The appearance of the product continued to be good without any signs ofaccretions or agglomerates. As before the only exception to this was theodd piece of scale type material, which appeared to be composed ofash/char.

The standard operating conditions and results during this period were asfollows.

CFB temperatures: 952° C. bottom and 940° C. top

Fluidising gas flowrate: 350 Nm³/hr (N₂) and 40 Nm³/hr

Pressure drop CFB: 80-100 mbar

Oxygen flowrate: 112 Nm³/hr

N₂ shield gas flowrate: 30 Nm³/hr

Coal Feed Rate: 430 kg/hr

Iron Ore Feed Rate: 20 kg/hr

A summary of the results is as follows:

Bed Discharge Rate: 125 kg/hr

Cyclone 3 Discharge: 15 kg/hr

Offgas Analysis

CO/CO₂ 11.5/9.6 = 1.2 % H₂ 14.1 % CH₄  2.6

Product Analysis: (0900 11 Dec. 2003)

Mass % Fe(T) Fe²⁺ Fe° % Met. Magnetic 9 58.2 15.5 42.35 72.8Non-Magnetic 91 1.74

11 Dec. 2003 1200-11 Dec. 2003 0600: Iron Ore at 40 kg/hr

Summary:

The iron ore feed rate was increased up to 40 kg/hr at 1200 on 11 Dec.2003 and operated with this rate until 0600 11 Dec. 2003, while thehydrogen gas rate was maintained at 40 Nm³/hr and the coal rate wasaround 360-420 kg/hr. The operation continued to be smooth without anydisruptions and the iron product discharge was highly metallised. Dustmake was also low with less than 10% of the total discharge coming fromthe final cyclone (i.e. cyclone 3). The vessel bed ΔP was beingmaintained at about 90-135 mbar and the temperature profile had a rangeof less than 10° C. between the bottom and the top of the bed.

Results

The appearance of the product continued to be good without any signs ofaccretions or agglomerates.

The standard operating conditions and results during this period were asfollows.

CFB temperatures: 953° C. bottom and 941° C. top

Fluidising gas flowrate: 370 Nm³/hr (N₂) and 40 Nm³/hr (H₂)

Pressure drop CFB: 98-130 mbar

Oxygen flowrate: 113 Nm³/hr

N₂ shield gas flowrate: 30 Nm³/hr

Coal Feed Rate: 426 kg/hr

Iron Ore Feed Rate: 40 kg/hr

A summary of the results is as follows:

Bed Discharge Rate: 190-210 kg/hr

Cyclone 3 Discharge: 15-20 kg/hr

Offgas Analysis

CO/CO₂ 9.9/11.4 = 0.87 % H₂ 12.9 % CH₄  2.9

Product Analysis: (11 Dec. 2003)

Mass % Fe(T) Fe²⁺ Fe° % Met. % Fe° in Prod 1500 Magnetic 30 74.38 14.5957.44 77.2 25.8 11 Dec. 2003 Non-magnetic 70 4.95 1900 Magnetic 34.871.56 19.33 50.75 70.9 26.8 11 Dec. 2003 Non-magnetic 65.2 2.98 2300Magnetic 27.4 66.4 20.22 45.66 68.8 21.1 11 Dec. 2003 Non-magnetic 72.64.03 0200 Magnetic 24.6 67.1 22.1 42.53 63.4 19.7 12 Dec. 2003Non-magnetic 75.4 4.3 0600 Magnetic 19.6 68.86 22.55 43.48 61.8 15.7 12Dec. 2003 Non-magnetic 80.4 2.73

The high metallisation achieved (70-77%) indicates that the oxygen lance(even at its 1.9-m position) did not penetrate too far to the bottom ofthe bed and that there was good segregation within the bed. The lowerpart of the bed is iron rich. The higher part of the bed is carbon richand this is interacting with the oxygen lance to generate heat and thisheat is then transferred back into the bed by the recirculation of thesolids to the lower parts of the bed. The low CO/CO₂ ratio in theoff-gas indicates achievement of high post combustion, with the energylevels being transferred back into the bed, while maintaining highmetallisation levels in the product discharge.

The iron levels in the product and the degree of metallisation indicatesthat the 700-mm vessel can be operated in gasification mode with up to20-25% metallic iron content without any problems with accretions. Thisis a significant achievement.

Oxygen Lance Inspection (11 Dec. 2003)

The lance was taken out of the 700-mm vessel and inspected on 11 Dec.2003.

In summary, the lance was clean. The water cooled pipe as well as thenozzle tip had no evidence of any buildup of material.

The lance was repositioned in the vessel at a higher position i.e. 3.8-mabove the distributor plate. The vessel was restarted with coal andoxygen and then once stabilised iron ore and hydrogen.

Operation with Iron Ore (110-200 kg/hr), Coal and Oxygen (lance 4-mheight) 13 Dec. 2003-16 Dec. 2003

13 Dec. 2003 0600-13 Dec. 2003 1200: Iron Ore at 110 kg/hr

Summary:

The iron ore feed rate was increased stepwise up to 110 kg/hr at 0625 on13 Dec. 2003 and operated with this rate until 1200 13 Dec. 2003 whilethe hydrogen gas rate was also increased stepwise up to 110 Nm³/hr overa 2 hr period. The coal rate was around 360-400 kg/hr. The operationcontinued to be smooth without any disruptions and the iron productdischarge from the vessel was up to 78% metallised. Dust make was alsolow with <10% of the total discharge coming from the final cyclone (i.e.cyclone 3). The vessel bed ΔP was being maintained at about 90-135 mbarand the temperature profile had a range of less than 5° C. between thebottom and the top of the bed.

Increasing the lance height from 1.9 m to 3.8 m did not seem to impacton the bed temperature profile. In fact, the temperature spread was lessthan 5° C. from top to bottom.

Results:

The appearance of the product continued to be good without any signs ofaccretions or agglomerates.

The standard operating conditions and results during this period were asfollows.

CFB temperatures: 953° C. bottom and 951° C. top

Fluidising gas flowrate CFB 10 Nm³/hr (N₂) at 860° C., 110 Nm³/hr (N₂)at 740° C., 180 Nm³/hr (N₂) at 680° C., and 110 Nm³/hr (H₂) at 860° C.

Pressure drop CFB: 80-100 mbar

Oxygen flowrate: 110 Nm³/hr

N₂ shield gas flowrate: 30-40 Nm³/hr

Coal Feed Rate: 360-400 kg/hr

Iron Ore Feed Rate: 110 kg/hr

A summary of the results is as follows:

Bed Discharge Rate: 162 kg/hr

Cyclone 3 Discharge: 16 kg/hr

Offgas Analysis

CO/CO₂ 10.9/9.6 = 1.14 % H₂ 19.6 % CH₄  2.3

Product Analysis: (13 Dec. 2003)

Mass % Fe(T) Fe²⁺ Fe° % Met. 1200 Magnetic 37.8 76.42 14.98 59.33 77.613 Dec. 2003 Non- 62.2 2.66 magnetic

With the higher oxygen lance position the uniform bed temperatureprofile of the lower lance was maintained. This indicates that even withthe oxygen lance at the 3.8 m position the solids recirculation profileis such that enough heat is transferred back into the bottom of the bed.

The temperature profile in the vessel and the cyclones indicated thatthere was probably no increase in dust make with the increase in ironore feed rate up to 110 kg/hr. The discharge from the final cyclonerelative to the vessel also did not change significantly. This suggeststhat either the iron ore is not breaking down as much as predicted orthat any fines generated are re-agglomerated in the high temperatureregion of the oxygen lance.

13 Dec. 2003 1200-16 Dec. 2003 0500: Iron Ore at 120-230 kg/hr

Summary:

For the first period of this operation from 17:00 13 Dec. 2003 to 12:0015 Dec. 2003 the operation rate was approximately 120 kg/h iron orefeed. This included a period of disturbance where there was no feed. Thefinal period operated at approximately 230 kg/h iron ore feed.

The operation with 230 kg/hr iron ore feed rate was smooth without anydisruptions and the iron product discharge from the CFB ranged from 48%to 78% metallised. Dust make was also low at <10% of the totaldischarge, coming from cyclone 3. The vessel bed ΔP was being maintainedat about 80-100 mbar and the temperature profile range had now increasedto about 20° C. between the bottom and the top of the bed.

Operating the vessel at the higher iron ore feed rate of 200 kg/hrincreased the range of the CFB temperature profile with the bottom partof the bed now being up to 20° C. colder than the middle of the bed. Themetallisation levels were also lower at the higher iron ore feed ratesbut they were still in the 60-80% metallisation range.

Results:

The appearance of the product continued to be good without any signs ofaccretions or agglomerates.

The standard operating conditions and results during this period were asfollows.

CFB temperatures: 947° C. bottom and 960° C. top

FB gas heater temperature: 740° C. and 615° C. main heater

Fluidising gas flowrate CFB: 20 Nm³/hr (N₂) at 840° C., 100 20 Nm³/hr(N₂) at 740° C., 185 20 Nm³/hr (N₂) at 615° C., and 140 Nm³/hr (H₂) @840° C.

Pressure drop CFB: 83-96 mbar

Oxygen flowrate: 113 Nm³/hr

N₂ shield gas flowrate: 30-40 Nm³/hr

Coal Feed Rate: 380 kg/hr

Iron Ore Feed Rate: 200 kg/hr

A summary of the results is as follows:

Bed Discharge Rate: 227-286 kg/hr

Cyclone 3 Discharge: 18-24 kg/hr

Offgas Analysis (0400 hrs 15 Dec. 2003)

CO/CO₂ 11/10.4 = 1.06 % H₂ 16.5 % CH₄  1.4

Product Analysis: (13-15 Dec. 2003)

Mass % C(T) Fe(T) Fe²⁺ Fe° % Met. 1700 Magnetic 40.2 — 75.55 22.1 51.3768.0 13 Dec. 2003 Non-magnetic 59.8 — 8.11 2000 Magnetic 54.2 1.8 78.3515.33 61.18 78.1 13 Dec. 2003 Non-magnetic 45.8 80.3 5.03 1700 Cyclone 312.89 2.73 2.47 19.2 13 Dec. 2003 discharge 2000 Cyclone 3 15.74 3.126.67 42.4 13 Dec. 2003 Discharge 0200 Magnetic 51.3 — 78.85 19.6 58.8774.7 15 Dec. 2003 Non-magnetic 48.7 — 7.29 0500 Magnetic 57.2 — 77.4417.27 57.65 74.4 15 Dec. 2003 Non-magnetic 42.8 — 4.55 0700 Magnetic62.8 0.9 76.93 17.38 58.43 75.9 15 Dec. 2003 Non-magnetic 37.2 72.511.25 0200 Cyclone 3 20.29 7.77 5.38 26.5 15 Dec. 2003 Discharge 0500Cyclone 3 21.73 7.69 6.28 28.9 15 Dec. 2003 Discharge 12:00 Magnetic59.2 — 76.9 18.1 56.6 73.6 15 Dec. 2003 Non-Magnetic 40.8 — 31.0 4.722.0 70.9 16:00 Magnetic 62.7 1.9 73.6 32.5 36.0 48.9 15 Dec. 2003Non-Magnetic 37.3 53.6 27.6 8.4 13.2 48.0 22:00 Magnetic 59.6 — 71.528.0 39.0 54.5 15 Dec. 2003 Non-Magnetic 40.4 — 20.4 3.9 11.0 54.0 02:00Magnetic 53.3 — 74.1 26.8 43.5 58.7 16 Dec. 2003 Non-Magnetic 46.7 —13.7 3.7 2.8 20.1 04:00 Magnetic 62.7 1.6 74.4 29.5 40.0 53.8 16 Dec.2003 Non-Magnetic 37.3 63.8 16.8 5.7 5.4 32.2

At the high iron ore feed rates (200 kg/hr) the discharge from thevessel increased significantly while the discharge from the finalcyclone only increased slightly. However, the discharge from the finalcyclone relative to the vessel did not seem to change. It was furtherobserved that the amount of fines <0.1 mm in the discharge was lowerthan the amount of fines <0.1 mm in the feed. This suggests that eitherthe iron ore is not breaking down as much as predicted or that any finesgenerated are re-agglomerated in the high temperature region of theoxygen lance. The temperature profile through the cyclones also supportsthis since there were no significant increases in temperatures throughthe cyclone system at the higher iron ore feed rates. The productmetallisation levels were maintained in the range of 68-78% during thehigh iron ore feed rates while the product discharge had up to 48%metallic iron.

Oxygen Lance and Vessel Inspection (16 Dec. 2003 and 19 Dec. 2003)

The lance was taken out of the 700-mm vessel and inspected on 16 Dec.2003. In summary, the lance was fairly clean. The water cooled pipe hada thin coating of material while the nozzle tip was relatively clean.The nature of the build up (flaky and thin) suggested that this wouldnot lead to any operational problems.

Iron Distribution & Agglomeration

Analysis of the Brockman ore sample used as feed to the fluidised bedindicated a fines content of approximately 10.6% sub 45 micron. Theseunits were expected to appear as output from cyclone 3 or as thickenersludge. Due to the friable nature of Brockman Ore, it was expected thatadditional fines would be produced during processing. It was thereforeexpected that the percentage of iron units exiting the system throughcyclone 3 would exceed 10.6%.

It was observed that approximately 7% of the iron units input to thefluidised bed were discharged through cyclone 3, either as direct outputfrom cyclone 3 (approximately 4%) or as output from the radial flowscrubber (approximately 3%). Analysis of the main product output fromthe fluidised bed indicated that an agglomeration mechanism was presentwithin the process. This mechanism appeared to be primarily smallerparticles, typically sub 100 micron particles, agglomerating to eachother and larger particles.

Many modifications may be made to the embodiments of the presentinvention shown in FIGS. 1 and 2 without departing from the spirit andscope of the invention.

1. A circulating fluidized bed process for direct reduction of ametalliferous material which comprises supplying the metalliferousmaterial, a solid carbonaceous material, an oxygen-rich gas, and afluidizing gas into a fluidized bed in a vessel and maintaining thefluidized bed in the vessel, at least partially reducing metalliferousmaterial in the vessel, and discharging a product stream that comprisesthe at least partially reduced metalliferous material from the vessel,comprising: (a) reducing the metalliferous material in a solid state ina metal-rich zone in the vessel; (b) injecting the oxygen-rich gas intoa carbon-rich zone in the vessel with a downward flow in a range of upto 40 degrees to the vertical and generating heat by reactions betweenoxygen and the metalliferous material, the solid carbonaceous materialand other oxidizable solids and gases in the fluidized bed, and (c)transferring heat from the carbon-rich zone to the metal-rich zone bymovement of solids within the vessel, and wherein the vessel has anupper section, a lower section, and an intermediate section, theintermediate section is intermediate said lower section and said uppersection of the vessel, and the metal-rich zone is formed in the lowersection of the vessel and the carbon-rich zone is formed in theintermediate section of the vessel, the oxygen-rich gas is injected intothe carbon-rich zone in the vessel at a location that is spacedhorizontally from walls of the vessel using a water-cooled lance, theprocess comprises withdrawing gas and entrained solids from the uppersection of the vessel, separating solids from the withdrawn gas, andrecirculating the separated solids to the vessel, the metalliferousmaterial and the solid carbonaceous material are supplied to thefluidized bed through a common solids delivery device, the oxygen-richgas comprises at least 90% by volume oxygen, and the metalliferousmaterial is supplied into the fluidized bed as particles that aredistinct from the carbonaceous material.
 2. A process according to claim1, comprising injecting the oxygen-containing gas into a central regionin the vessel.
 3. A process according to claim 1, comprising controllingoperation such that the temperature difference between the bulktemperature in the fluidized bed and the average temperature of theinwardly facing surface of a side wall of the vessel is no more than100° C.
 4. A process according to claim 1, wherein the metalliferousmaterial is in the form of iron ore fines, and the bulk temperature inthe fluidized bed is in the range 850° C. to 1000° C.
 5. A processaccording to claim 4, wherein the bulk temperature in the fluidized bedis at least 900° C.
 6. A process according to claim 1, comprisingcontrolling operation such that the temperature variation is less than50° C. within the fluidized bed.
 7. A process according to claim 1,wherein the metalliferous material is in the form of iron ore fines, andthe pressure in the vessel is controlled to be in the range of 1-10 barabsolute.
 8. A process according to claim 1, comprising injecting theoxygen-rich gas via at least one lance having a lance tip with an outletpositioned in the vessel inwardly of the side wall of the vessel in thecentral region of the vessel.
 9. A process according to claim 8, whereinthe lance tip is directed vertically downwardly.
 10. A process accordingto claim 8, wherein at least the lance tip is water-cooled.
 11. Aprocess according to claim 8, wherein an outer surface of the lance iswater-cooled.
 12. A process according to claim 8, wherein theoxygen-rich gas is injected through a central pipe of the lance.
 13. Aprocess according to claim 8, wherein the oxygen-rich gas is injectedwith sufficient velocity to form a substantially solids-free zone in theregion of the lance tip.
 14. A process according to claim 8, comprisinginjecting a shrouding gas for shrouding the region of the outlet of thelance tip.
 15. A process according to claim 14, wherein the shroudinggas is injected into the vessel at a velocity that is at least 60% ofthe velocity of the oxygen-containing gas.
 16. A process according toclaim 1, comprising supplying the metalliferous feed material, thecarbonaceous material, the oxygen-rich gas, and the fluidizing gas tothe fluidized bed and maintaining the fluidized bed with (a) a downwardflow of the oxygen-rich gas, (b) an upward flow of solids and fluidizinggas countercurrent to the downward flow of the oxygen-rich gas, and (c)a downward flow of solids outwardly of the upward flow of solids andfluidizing gas.
 17. A process according to claim 16, comprising heatingsolids in the upward and downward flows of solids by heat generated byreactions between the oxygen-rich gas, the solid carbonaceous materialand other oxidizable materials in the carbon-rich zone.
 18. A processaccording to claim 16, wherein the upward and downward flows of solidsshield the side wall of the vessel from radiant heat generated byreactions between the oxygen-rich gas and the solid carbonaceousmaterial and other oxidizable solids and gases in the fluidized bed. 19.A process according to claim 1, wherein the metalliferous material is inthe form of iron ore fines sized at minus 6 mm.
 20. A process accordingto claim 19, wherein the fines have an average particle size in therange of 0.1 to 0.8 mm.
 21. A process according to claim 1, wherein thecarbonaceous material is coal.
 22. A process according to claim 1,wherein the fluidizing gas comprises a reducing gas.
 23. A processaccording to claim 22, wherein the fluidizing gas comprises CO and H₂and the amount of H₂ in the fluidizing gas is at least 15% by volume ofthe total volume of CO and H₂ in the gas.
 24. A process according toclaim 1, wherein the product stream comprising at least partiallyreduced metalliferous material is discharged from the lower section ofthe vessel.
 25. A process according to claim 24, wherein the productstream also comprises other solids, and the process comprises separatingat least a portion of the other solids from the product stream.
 26. Aprocess according to claim 25, wherein the separated solids are returnedto the vessel.
 27. A process according to claim 1, comprising returningthe separated solids to the lower section of the vessel.
 28. A processaccording to claim 1, wherein metalliferous feed material is preheatedwith the off-gas from the vessel.
 29. A process according to claim 28,wherein the off-gas is treated after the preheating step and at least aportion of the treated off-gas is returned to the vessel as thefluidizing gas.
 30. A process according to claim 29, wherein the off-gastreatment comprises one or more of (a) solids removal, (b) cooling, (c)H₂O removal, (d) CO₂ removal, (e) compression, and (f) reheating.
 31. Aprocess according to claim 29, wherein the off-gas treatment comprisesreturning solids to the vessel.
 32. A process according to claim 1,wherein the metallization of the product stream is greater than 50%, andthe process comprises operating with reducing gas in the fluidizing gas.33. A process according to claim 1, comprising an additional smeltingprocess for melting and further reducing the partially reducedmetalliferous material to a molten metal.
 34. A process according toclaim 1, comprising returning the separated solids to the intermediatesection of the vessel.
 35. A circulating fluidized bed process fordirect reduction of a metalliferous material which comprises: supplyingthe metalliferous material and a solid carbonaceous material into avessel above a lower end region of the vessel through a common solidsdelivery device, wherein the metalliferous material is supplied into thevessel as particcles that are distinct from the carbonaceous materialsupplying a fluidizing gas into the vessel at the lower end region ofthe vessel for maintaining a fluidized bed in the vessel, wherein themetalliferous material is supplied into the vessel as particles that aredistinct from the carbonaceous material, injecting an oxygen-rich gascomprising at least 90% by volume oxygen into the vessel at a locationabove that at which the solid carbonaceous material is supplied to thevessel with a downward flow in a range of up to 40 degrees to thevertical using a water-cooled lance, withdrawing gas and entrainedsolids from an upper section of the vessel, separating solids from thewithdrawn gas, recirculating the separated solids to the vessel, anddischarging a product stream from the lower end region of the vessel,whereby the oxygen-rich gas is directed into a carbon-rich zone in thevessel at a location that is spaced horizontally from walls of thevessel and heat is generated in the carbon-rich zone by reactionsbetween oxygen and at least the solid carbonaceous material, heat istransferred from the carbon-rich zone to a metal-rich reducing zone inthe lower end region of the vessel by movement of solids within thevessel, metalliferous material in the solid state is at least partiallyreduced in the reducing zone, and the product stream that is dischargedfrom the lower end region of the vessel comprises the at least partiallyreduced metalliferous material.
 36. A process according to claim 35,comprising returning the separated solids to the intermediate section ofthe vessel.
 37. A circulating fluidized bed process for direct reductionof a metalliferous material, comprising: providing a vessel having anupper section, a lower section, and an intermediate section, theintermediate section being intermediate said lower section and saidupper section of the vessel, supplying the metalliferous material and asolid carbonaceous material to the intermediate section of the through acommon solids delivery device, wherein the metalliferous material issupplied to the vessel as particles that are distinct from thecarbonaceous material, injecting an oxygen-rich gas comprising at least90% by volume oxygen downwardly into the intermediate section of thevessel at a location that is horizontally spaced from walls of thevessel using a water-cooled lance, injecting a fluidizing gas into thelower section of the vessel, the fluidizing gas being a reducing gas,withdrawing gas and entrained solids from the upper section of thevessel, separating solids from the withdrawn gas, recirculating theseparated solids to the vessel, and discharging a product stream fromthe lower section of the vessel, whereby injection of the fluidizing gasestablishes and maintains a fluidized bed in the vessel and creates areducing region in the lower section of the vessel in whichmetalliferous material is at least partially reduced in the solid state,injection of the oxygen-rich gas into the intermediate section of thevessel creates an oxidizing region in the intermediate section of thevessel in which heat is generated by reactions between oxygen and themetalliferous material, the solid carbonaceous material and otheroxidizable solids and gases in the fluidized bed, movement of solidswithin the vessel transfers heat from the oxidizing region to thereducing region, and the product stream comprises the at least partiallyreduced metalliferous material.
 38. A method according to claim 37,comprising treating the withdrawn gas to remove H₂O and CO₂ andinjecting the treated gas into the lower section of the vessel asfluidizing gas.
 39. A method according to claim 37 comprising scrubbingthe withdrawn gas to remove residual solids, dewatering the scrubbedgas, and combusting the dewatered gas.
 40. A method according to claim37, comprising melting and further reducing the product streamdischarged from the lower section of the vessel.
 41. A process accordingto claim 37, comprising returning the separated solids to theintermediate section of the vessel.